Bonding apparatus and bonding method

ABSTRACT

To provide a bonding apparatus capable of increasing product quality by realizing high-precision control of a pressing force applied upon mounting of an electronic component on a substrate by bonding, and to a bonding method capable of providing high-quality products stably. The bonding apparatus includes: at least a bonding head  100  for pressing an electronic component  6  against a substrate  1  to bond it to the substrate  1 ; a plurality of load detection mechanisms (e.g., load sensors  5 ) substantially equally spaced so as to face one another under a substrate stage S supporting the substrate  1  provided with the electronic component  6 ; and a pressure detection unit  20  for detecting pressing force at the bonding surface between the electronic component  6  and substrate  1  on the basis of the pressure values detected by the individual load detection mechanisms  5.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/503,907, filed on Aug. 15, 2006 which is based upon and claims thebenefits of the priority from the prior Japanese Patent Application No.2006-075375 filed on Mar. 17, 2006, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bonding apparatus capable ofincreasing product quality by realizing high-precision control of apressing force applied upon mounting of an electronic component on asubstrate by bonding, and to a bonding method capable of providinghigh-quality products stably.

2. Description of the Related Art

Electronic devices (e.g., computers) have become faster and smaller, andthere is an increasing demand for high-density packaging of electroniccomponents. Against this background, substrates for large scaleintegration have been used, in which a plurality of electroniccomponents is arranged on a substrate in layers. In addition, fortighter packing of electronic components, flip-chip bonding has beenemployed in which bumps are formed on an electronic component that is tobe mounted on a substrate, and the bumps are then pressed against thesubstrate and welded thereto. High pin count and device miniaturizationhave been realized in this approach, with an increasing demand forreduced bump diameter and reduced pitch between bump connectionterminals.

However, if bump connection terminal pitch reaches as small as 40 μm orless, a concern arises regarding the occurrence of connection defects,such as short-circuits between terminals, and damages to the electriccomponent if it fails to achieve high-precision positioning (tolerancesto ±1 μm) and/or stable load control because of variations in thefabrication precision of the substrate and in the formation of bumps.Short circuits between terminals occur due to, for instance, excessivelycrushed bumps and displacement after recognition. Damages to theelectronic component include failures of, for example, bumps andterminals of the electronic component and substrate.

The following bonding apparatus has been conventionally used forelectronic component bonding: A bonding apparatus which has a bondingtool provided so as to be capable of moving up and down, and a loadsensor for detecting load that has been applied to an electroniccomponent by the bonding tool. In such a bonding apparatus the loadsensor is provided on the upper side of the bonding tool support and theload sensor is allowed to contact the bonding tool support to cause botha bonding head attached with the bonding tool and load sensor to movedown, bonding the electronic component to the substrate. The bondingapparatus is so configured that, at this point, load (pressing force)applied by the bonding tool is detected by the load sensor that is incontact with the bonding tool.

The followings are specific examples of conventional bonding apparatusused: A bonding apparatus in which a bonding tool support is suspendedfrom a head unit by a spring (see Japanese Patent Application Laid-Open(JP-A) No. 2000-183114); a bonding apparatus equipped with two differentload detection mechanisms: one configured to detect decreasing load, andone configured to detect increasing load, at a time when a given levelof load applied to a bonding tool support has caused a bonding tool topress an electronic component (see Japanese Patent Application Laid-Open(JP-A) No. 2002-76061); a bonding apparatus configured to carry outfeedback control by previously creating a given level of thrust in acylinder (see Japanese Patent Application Laid-Open (JP-A) No.2001-68895); and a bonding apparatus in which a bonding head is providedwith a parallelism adjustment mechanism by which the parallelism of abonding tool is determined by a parallelism detection sensor (seeJapanese Patent Application Laid-Open (JP-A) No. 2001-223244). However,when high-precision positioning and high-precision load control arerequired in connection with reduced pitch between bump connectionterminals, variations occur in the in-plane stress due to variations inthe precision of components (e.g., substrates and bumps), even thoughthe detected load values falls within a set reference load for a bondingoperation, leading to reduced product yields due to connection failuresand the like.

With respect to the set reference load—a whole pressure created during abonding operation—there arises the following problem: The bonding toolsupport is provided with a number of components: mechanical sections(e.g., slide guides, a shaft, a cylinder and a spring) that constitute alifting and lowering mechanism; mechanical sections for attaching andcooling an electronic component and for adjusting the inclination of theelectronic component; and a number of parts (e.g., wires and pipes) forconnecting these mechanical sections together. Thus, in a case of a loadsensor provided on the upper side of the bonding tool support, availablelocations or areas for the load sensor are limited. In addition, theload sensor is susceptible to heat generated due to friction of thecomponents and thus tends to produce different values for the detectedload. The measured pressure value only means the load applied to thebonding tool support, and includes escaping loads such as inclined loadsacting on the components, and horizontal components. For this reason,the measured load value is not necessarily equal to the value for loadacting on the bonding portions, thus requiring periodical loadcalibration.

Accordingly, bonding apparatuses with conventional load detectionmechanisms, as disclosed in the foregoing Patent Literatures, cannotachieve further increase in the product quality; therefore, bondingtechnology has been sought after that enables high-precision pressingforce control for increased product quality.

It is an object of the present invention to solve the foregoingconventional problems and to achieve the object described below.

Specifically, it is an object of the present invention to provide abonding apparatus capable of increasing product quality by realizinghigh-precision control of a pressing force applied upon mounting of anelectronic component on a substrate by bonding, and to a bonding methodcapable of providing high-quality products stably.

SUMMARY OF THE INVENTION

The following is the means for solving the foregoing problems:

The bonding apparatus of the present invention includes at least: abonding head configured to press an electronic component against asubstrate to bond the electronic component to the substrate; a pluralityof load detection mechanisms that are substantially equally spaced so asto face one another under a substrate stage which supports the substratearranged to face the electronic component; and a pressure detection unitconfigured to detect a pressure on a bonding surface between theelectronic component and the substrate on the basis of pressure valuesdetected by the individual load detection mechanisms.

In this bonding apparatus the plurality of load detection mechanisms isprovided under the substrate stage in such a way that they aresubstantially equally spaced so as to face one another, for example, ina matrix form. For this reason, spaces on a planar surface where suchload detection mechanisms are arranged can be more readily secured inthe bonding apparatus of the present invention than in conventional oneswhere the load detection mechanisms are arranged in the vicinity of thebonding tool support. In addition, there are no complex componentsaround the load detection mechanisms and there is no need to move up ordown them, thus allowing detection of the net load applied to thesubstrate stage. Furthermore, the provision of the plurality of loaddetection mechanisms allows measurement of the pressure distributed overthe substrate stage surface and high-precision control of a pressingforce of the bonding head. Thus, it is possible to increase productquality.

The bonding method of the present invention includes at least a pressingstep of pressing an electronic component against a substrate by means ofa bonding head to bond the electronic component to the substrate; and apressure detection step of detecting a pressure at a bonding surfacebetween the electronic component and the substrate on the basis ofpressure values detected by a plurality of load detection mechanismsthat are substantially equally spaced so as to face one another under asubstrate stage which supports the substrate arranged to face theelectronic component.

With this bonding method, in the pressing step, the electronic componentis first pressed against the substrate by means of the bonding head andis thereby bonded to the substrate. In the pressure detection step, thepressure at a bonding surface between the electronic component and thesubstrate is detected on the basis of pressure values detected by aplurality of load detection mechanisms that are substantially equallyspaced so as to face one another under a substrate stage which supportsthe substrate arranged to face the electronic component. As a result,the net load applied to the substrate stage is detected, the pressuredistributed over the substrate stage surface is measured, and thepressing force of the bonding head is controlled with high precision.Thus, it is possible to stably provide high-quality products with highyields.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view for explaining a schematicconfiguration of a bonding apparatus of a first embodiment of thepresent invention.

FIG. 2 is a plan view for explaining a schematic configuration of a loaddetection mechanism in the bonding apparatus of the first embodiment ofthe present invention.

FIG. 3A is a first schematic explanatory diagram of an example of amodification of the load detection mechanism in the bonding apparatus ofthe first embodiment of the present invention.

FIG. 3B is a second schematic explanatory diagram of an example of amodification of the load detection mechanism in the bonding apparatus ofthe first embodiment of the present invention.

FIG. 3C is a third schematic explanatory diagram of an example of amodification of the load detection mechanism in the bonding apparatus ofthe first embodiment of the present invention.

FIG. 4 is a flowchart for explaining an operation (bonding method) ofthe bonding apparatus of the first embodiment of the present invention.

FIG. 5A is a first schematic explanatory diagram showing a bondingoperation by means of a bonding method using the bonding apparatus ofthe first embodiment of the present invention.

FIG. 5B is a second schematic explanatory diagram showing the bondingoperation by means of a bonding method using the bonding apparatus ofthe first embodiment of the present invention.

FIG. 6A is graph showing an example of a plot of reference load vs. timein the bonding apparatus of the first embodiment of the presentinvention.

FIG. 6B is graph showing an example of a plot of load vs. time, the loaddetected by an individual load sensor of the bonding apparatus of thefirst embodiment of the present invention.

FIG. 7A is a first schematic explanatory diagram showing an example oftrouble that occurs during a bonding operation carried out by means ofthe bonding method using the bonding apparatus of the first embodimentof the present invention.

FIG. 7B is a second schematic explanatory diagram showing an example oftrouble that occurs during a bonding operation carried out by means ofthe bonding method using the bonding apparatus of the first embodimentof the present invention.

FIG. 7C is a third schematic explanatory diagram showing an example oftrouble that occurs during a bonding operation carried out by means ofthe bonding method using the bonding apparatus of the first embodimentof the present invention.

FIG. 7D is a fourth schematic explanatory diagram showing an example oftrouble that occurs during a bonding operation carried out by means ofthe bonding method using the bonding apparatus of the first embodimentof the present invention.

FIG. 7E is a fifth schematic explanatory diagram showing an example oftrouble that occurs during a bonding operation carried out by means ofthe bonding method using the bonding apparatus of the first embodimentof the present invention.

FIG. 7F is a sixth schematic explanatory diagram showing a example oftrouble that occurs during a bonding operation carried out by means ofthe bonding method using the bonding apparatus of the first embodimentof the present invention.

FIG. 8A is a first graph showing another plot of load vs. time, theloads detected by the individual load sensors of the bonding apparatusof the first embodiment of the present invention.

FIG. 8B is a second graph showing still another plot of load vs. time,the loads detected by the individual load sensors of the bondingapparatus of the first embodiment of the present invention.

FIG. 9A is a first step view for explaining a substrate transportationoperation carried out in the bonding apparatus of the first embodimentof the present invention.

FIG. 9B is a second step view for explaining the substratetransportation operation carried out in the bonding apparatus of thefirst embodiment of the present invention.

FIG. 9C is a third step view for explaining the substrate transportationoperation carried out in the bonding apparatus of the first embodimentof the present invention.

FIG. 9D is a fourth step view for explaining the substratetransportation operation carried out in the bonding apparatus of thefirst embodiment of the present invention.

FIG. 10A is a cross-sectional view for explaining an example of theschematic configuration of a conventional bonding apparatus.

FIG. 10B is a cross-sectional view for explaining another example of theschematic configuration of a conventional bonding apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the bonding apparatus and bonding method of the presentinvention will be described in detail with reference to the drawings.

Embodiment 1

The first embodiment of the bonding apparatus of the present inventionwill be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing a schematic configuration ofthe bonding apparatus according to the first embodiment of the presentinvention.

The bonding apparatus shown in FIG. 1 is one carrying out flip chipbonding, and has a bonding head 100. The bonding head 100 has a functionof heating and pressurizing (pressing) an electronic component havingbumps to bond the bumps to connection terminals of a substrate 1.

As shown in FIG. 1, the bonding head 100 includes a bonding tool support10 having a bonding tool 7 which operates by attaching thereto anelectronic component 6 by vacuum and a heat mechanism 8 for heating thebonding tool 7 to heat bumps 6A formed on the electronic component 6 tothereby set bonding temperature to about 180° C. to 350° C. In thebonding tool support 10, a protruding part 10A is engaged with acylinder 11 attached to a C-shaped lifting and lowering block 12, and isheld by the lifting and lowering block 12 via a slidable slide guide 9.In addition, a θ motor 13 is arranged on the top of the bonding toolsupport 10. The 0 motor 13 carries out a 0 rotation correction uponpositioning of the electronic component 6.

Note that the cylinder 11 may be used without changing its thrust or maybe used while changing its thrust by means of a later-described pressureadjustment unit 22 (e.g., an electropneumatic regulator), which makescylinder thrust variable by feedback control.

The lifting and lowering block 12 is connected to a lifting and loweringmechanism 18 which is comprised of a slide guide 15, a feed screw 16,and a Z motor 17 arranged on the top of the feed screw 16, and the flatside wall of the C-shaped lifting and lowering block 12 is held by thefeed screw 16 via the slidable slide guide 15. When load is applied tothe electronic component 6 more than necessary, the lifting and loweringblock 12 connected to the lifting and lowering mechanism 18 is allowedto move up and down for feedback control on the set load, protecting thesubstrate 1, electronic component 6, load sensor 5, etc. from damages.

The substrate 1 having connection terminals 1A formed thereon is placedon a substrate attachment plate 2 that holds the substrate 1 by vacuum.Under the substrate attachment plate 2, a substrate heater 3 for heatingthe substrate 1 and heat insulating material 4 are provided. The heatinsulating material 4 is supported by a matrix of four load sensors 5positioned at the four corners of the heat insulating material 4. Notein this embodiment that the substrate attachment plate 2, substrateheater 3 and heat insulating material 4 constitute a substrate stage S.

Signals from these load sensors 5 are then detected by a pressuredetection unit 20 (e.g., an A/D converter) and transmitted to a controlunit 21 for measurement of both the total load on the bumps 6A of theelectronic component 6 and the pressure distributed over the substratestage S surface and for control of the pressure adjustment unit 22. Inthis way, set load for bonding operations is controlled.

Conventionally, the rating of a load sensor is so determined that it cansupport a maximum set load adopted for a bonding apparatus; within aload range up to 490.33N (50 kgf), 490.33N (50 kgf) is generally adoptedfor the rating of load sensors for high-pressure detection, and 49.03N(5 kgf) for the rating of load sensors for low-pressure detection. Forthis reason, when a set load ranges from 49.03N (5 kgf) to 147.10N (15kgf), the load sensor is rated at 50 kgf, which results in poorprecision.

The bonding apparatus according to the first embodiment of the presentinvention, however, has four load sensors 5 and thus a maximum load isequally shared by them. For this reason, even when a maximum load of490.33N (50 kgf) is applied, the load on per one load sensor 5 isreduced by a factor of 4 (i.e., 122.58N (12.5 kgf)). Thus, it ispossible to increase the linearity of the hysteresis curve and/orhysteresis characteristics by reducing the ratings of the load sensors5.

The operation frequency of the lifting and lowering mechanism that hasthe slide guides, spring, cylinder, etc. is very high in view of theunits of the semiconductor device manufactured. The lifting and loweringmechanism is susceptible to heat generated due to friction of theforegoing complex components; thus, the status of the bonding apparatusis likely to change accordingly. The bonding apparatus according to thefirst embodiment of the present invention, however, has no complexlifting and lowering mechanism and has a matrix of the immobilized fourload sensors 5 under the substrate 1, allowing detection of the net loadapplied to the portions where the bumps 6A and corresponding connectionterminals 1A are bonded together, and of the pressure distributed overthe substrate stage S surface.

Next, the load detection mechanism in the bonding apparatus according tothe first embodiment of the present invention will be described. FIG. 2is a plan view showing the load detection mechanism in the bondingapparatus.

As shown in FIG. 2, the substrate 1 is attached by vacuum to thesubstrate attachment plate 2 that has a vacuum aspiration groovecorresponding to the shape of the substrate 1. The substrate heater 3for heating the substrate 1 is provided under the substrate attachmentplate 2, heating the substrate 1 to about 100° C. in general. The loadsensors 5 are provided under the substrate heater 3 with the heatinsulating material 4 interposed between them. The permissibletemperature range for the load sensors 5 generally ranges from about 50°C. to 100° C., and therefore, both the load sensors 5 and a drive unit(not shown) that moves the substrate stage S need to be protectedagainst heat (about 180° C. to 350° C.) generated upon heating of thesubstrate 1 and bonding of the electronic component 6. To this end, theheat insulating material 4 and a cooling mechanism (not shown) arearranged.

In this embodiment the four load sensors 5—the first load sensor 5A,second load sensor 5B, third load sensor 5C, and fourth load sensor5D—are substantially equally spaced along the perimeter of the substrateattachment plate 2 so as to face one another, forming a matrix of loadsensors provided at positions corresponding to the four corners of thesubstrate attachment plate 2, as shown in FIG. 2. The detection signalfrom each of the load sensors 5A to 5D is outputted to the control unit21 via the pressure detection unit 20 (e.g., an A/D converter).

The shape and locations of the load sensors 5 are not particularlylimited; various modifications can be made as described below. Forexample, as shown in FIG. 3A, the substrate stage S may be immobilizedby means of strain gauges as the load sensors 5. As shown in FIG. 3B,other mechanisms (e.g., load cells) as the load sensors 5 may becombined, and a guide part G may be provided to make the substrate stageS mobile. As shown in FIG. 3C, in addition to the foregoing load sensors5A to 5D, additional four load sensors—the fifth load sensor 5E, sixthload sensor 5F, seventh load sensor 5G, and eighth load sensor 5H—may beprovided in such a way that they are substantially equally spaced alongthe perimeter of the substrate attachment plate 2 so as to face oneanother in a matrix form. As shown in FIG. 3C, as the number of the loadsensor 5 increases (8 in FIG. 3C), so too does the number of loaddetection points, allowing acquisition of more detailed load detectiondata.

The bonding operation (bonding method of the present invention) carriedout by the bonding apparatus will be described with reference to theflowchart shown in FIG. 4.

As a pressure load (whole bonding load) applied to bond the connectionterminals 1A of the substrate 1 to the bumps 6A of the electroniccomponent 6, a reference pressure and the descending speed of thebonding tool 7 are set by the control unit 21 (e.g., a microcomputer).In this embodiment, pressure values detected by the load sensors 5A to5D are used to set the upper and lower thresholds for a pressing forceon each of the load sensors 5A to 5D. The thresholds are appropriatelydetermined according to the constitutional material, structure, size,etc. of the substrate 1, bumps 6A, etc. Alternatively, they can bedetermined by detecting either pressure acting on one load sensorpositioned at one corner of an electronic component or pressure actingon a side of the electronic component having a combination of loadsensors (i.e., pressure acting on a row of load sensors), on the basisof the pressure acting on one bump, data concerning the connectionterminal strength that results in defects, etc. Moreover, if thepressing force exceeds the thresholds, alarm notifications are sentand/or the apparatus operation is halted, enabling early notification ofthe occurrence of abnormalities.

As shown in FIG. 5A, in a bonding operation, the bonding tool 7 is moveddown by means of the lifting and lowering mechanism 18, so that bondingload has a reference pressure. In this way the electronic component 6attached to the bonding tool 7 by vacuum moves down toward theconnection terminals 1A formed on the substrate 1. As shown in FIG. 5B,pressure values, detected by the load sensors 5A to 5D during a periodfrom the time when the electronic component 6 and substrate 1 make firstcontact to the time when the bonding tool 7 is completely lifted after apredetermined period of a bonding operation, are transmitted to thecontrol unit 21. As shown in FIG. 4, the control unit 21 then comparesthe predetermined reference pressure with the total of the pressurevalues detected by the load sensors 1 to 4 (load sensors 5A to 5D) toperform feedback control on the pressure adjustment unit 22. In this waya digital flow rate-regulating valve is adjusted by a pressure motordriver to adjust the flow rate in the cylinder 11. The flow rate in thecylinder 11 is detected and transmitted to the control unit 21. Each ofthe detected pressure values thus sampled is compared with the upper andlower thresholds for the pressing force that have been previously setfor one corner and one side of the electronic component 6. When thedetected pressure values—even within the set reference pressure—exceededthese upper and lower thresholds, it is determined that abnormalitieshave occurred, followed by sending of alarm notification and halt of theapparatus operation. Thus, the electronic component 6 can be protectedfrom being damaged. Moreover, detected pressure values sampled for eachbonding operation can be monitored over time, stored as a manufacturestatus history. It is therefore possible to increase product quality andto ensure traceability of products.

Next, with reference to FIGS. 6A and 6B, description will be providedhow the load sensors 5A to 5D detect pressure.

A graph as shown in FIG. 6A is given by plotting the change in X, abonding load reference pressure (reference pressure per one electroniccomponent), versus time. The bonding load reference pressure equals tothe total of the pressure values, which have been detected by the loadsensors 5A to 5D during a period from the time when a reference pressureis applied to the electronic component 6 as a result of contact betweenthe electronic component 6 and substrate 1 to the time when the bondingtool 7 is completely lifted after a predetermined period of a bondingoperation.

When the load sensors 5A to 5D are equally pressed, X1, a detectedpressure value per one load sensor, is four times as small as thebonding load reference pressure X, as shown in FIG. 6B. This means thatload is equally distributed on the bumps 6A of the electronic component6. In this state, there is no concern for damages to the electroniccomponent 6.

Troubles that occur during a bonding operation are shown in FIGS. 7A to7F. In FIG. 7A, the bonding tool 7 is inclined and is out of parallelismrelative to the substrate stage S. In FIG. 7B, the substrate stage S isinclined and is out of parallelism relative to the bonding tool 7. InFIG. 7C, the bumps 6A are different in height. In either case,connection failures have occurred between the connection terminals 1Aand bumps 6A. In FIG. 7D, foreign material D is trapped between thesubstrate 1 and substrate stage S. In FIG. 7E, foreign material D istrapped between the electronic component 6 and bonding tool 7. In FIG.7F, foreign material D is trapped between the connection terminal 1A andbump 6A. In either case, connection failures have occurred. In addition,such connection failures occur due to, for example, variations in thesubstrate and in the chip thickness. Load detection mechanisms inconventional bonding apparatus cannot find such connection failures, anda bonding operation finishes after application of a bonding loadreference pressure X (total load reference pressure per one electroniccomponent) shown in FIG. 6B. In the first embodiment of the presentinvention, however, since thresholds are set for each of the pressurevalues detected by the plurality of load sensors 5, it is possible todetect abnormalities such as connection failures. As described above,with conventional loading detection mechanisms, no abnormalities can bedetected upon occurrence of component crash, connection failures, etc.,continuing manufacturing operations. More specifically, load to beapplied over the electronic component converges to a particular point,resulting in electronic component failure and reduced production yields.According to the present invention, however, it is possible to increaseproduct quality and production yields.

Even when such abnormalities are minor ones that disappear as the bumps6A of the electronic component 6 deform, the load sensors 5A to 5D inthis embodiment produce different values for the detected pressure,allowing detection of such minor abnormalities. To be more specific, forexample, when the bonding tool 7 and substrate stage S are out ofparallelism as shown in FIGS. 7A and 7B and accordingly the electroniccomponent 6 is inclined such that load is first applied to the loadsensors 5A and 5B shown in FIG. 2, the bonding apparatus is socontrolled that a bonding load reference pressure is applied to them ata predetermined rate. For this reason, the load detected by the loadsensors 5A and 5B increases first as indicated by X2 of FIG. 8A andlater on, as the bumps 6A deforms by application of pressure, load isalso applied to the load sensors 5C and 5D as indicated by X3.

Similarly, when the electronic component 6 is inclined such that load isapplied only to the load sensor 5A at an early stage, as shown in FIG.8B, the load detected by the load sensor 5A increases first as indicatedby X4. As the bumps 6A deforms by application of load, load is alsoapplied to the load sensors 5B and 5C as indicated by X5 and finally,load is applied to the load sensor 5D as indicated by X6. Variations inload values among the load sensors 5A to 5D begin to decrease from thetime when load is uniformly applied to them.

Thus, there is a time-lag before all of the load sensors 5A and 5D areuniformly pressed. However, the bonding apparatus according to thisembodiment can detect such a time lag. Load sensors that are firstpressed tend to produce higher values for the detected pressure thanother load sensors; therefore, loads acting on components (e.g., theelectronic component 6, bumps 6A, and connection terminals 1A on thesubstrate 1) are compared with the upper and lower thresholds for thepressing force that are previously set for one corner and one side ofthe electronic component 6, allowing monitoring whether components inthe resulting products have been fabricated within the allowablestrength range. Thus, it is possible to increase product quality andreliability.

In this embodiment, although a bonding operation has been made for oneelement on the substrate 1 as described above, similar bondingoperations can be made for a plurality of elements arranged on onesubstrate. For example, when four elements 31A to 31D are arranged on asubstrate 30 as shown in FIGS. 9A to 9D, the substrate stage may befixed and then the substrate 30 may be moved for the bonding ofindividual electronic components 6 in the order from FIG. 9A to FIG. 9D.Alternatively, in this case, the substrate stage may be divided intoseveral sections before performing bonding operations. These embodimentsare suitable for multiple bonding and, what is more, are mechanicallyallowable, for example, for semiconductor devices with high pin countand large-area semiconductor devices, which require high load during abonding operation.

With the bonding apparatus and bonding method of the present invention,a plurality of load sensors is arranged on a substrate in a matrix form.Load to a bonding portion, applied within the upper and lower thresholdsfor the allowable load that have been previously set for each positionwhere the load sensor detects load, is feedback-controlled, and thestress distribution over the substrate stage surface can be monitored.Thus, it is possible to increase the accuracy and reliability of theload detection mechanism upon bonding of the electronic component to thesubstrate (i.e., upon production of products).

Since it is possible to find during a bonding operation troubles (e.g.,inclination of the bonding tool, contamination of foreign material,variations in the level of bumps, connection failures betweensubstrate's connection terminals, abnormal lifting and lowering of thebonding tool, and wearing away and/or failure of the lifting andlowering mechanism), the occurrence of abnormalities and/or the presenceof defective pieces can be immediately determined, allowing a stableproduction management at all times without involving continuedproduction of defective pieces. Thus, it is possible to providehigh-quality products with high yields.

In addition, when abnormalities have occurred, alarms can be issued andthe operation of the apparatus can be halted, thus ensuring thetraceability of products for quality management.

Conventional Example

FIGS. 10A and 10B each shows a schematic configuration of a conventionalbonding apparatus.

The bonding apparatus shown in FIG. 10A includes a bonding head 200. Thebonding head 200 includes a bonding tool support 210 having a bondingtool 207 which operates by attaching an electronic component 206 byvacuum thereto and a heat mechanism 208 for heating the bonding tool 207to heat bumps 206A formed on an electronic component 206. In the bondingtool support 210, a protruding part 210A is engaged with a cylinder 211attached to a C-shaped lifting and lowering block 212, and the lowersurface of the protruding part 210A is biased against the lifting andlowering block 212 by a spring 230. The bonding tool support 210 is heldby the lifting and lowering block 212 via a slidable slide guide 209. Inaddition, a rotary motor 213 is arranged on the top of the bonding toolsupport 210. The rotary motor 213 carries out a rotation correction uponpositioning of the electronic component 206. A load sensor 205 fordetecting the pressing force of the bonding tool 207 is arranged on thebonding tool support 210 beneath the cylinder 211.

The lifting and lowering block 212 is connected to a lifting andlowering mechanism 218 which is comprised of a slide guide 215, a feedscrew 216, and a lifting and lowering motor 217 arranged on the top ofthe feed screw 216, and the flat side wall of the C-shaped lifting andlowering mechanism 212 is held by the feed screw 216 via the slidableslide guide 215. The lifting and lowering block 212 connected to thelifting and lowering mechanism 218 is allowed to move vertically,causing the bonding tool 207 to move vertically accordingly.

A substrate 201 having connection terminals 201A formed thereon isplaced on a substrate attachment plate 202 that holds the substrate 201by vacuum. Under the substrate attachment plate 202, a substrate heater203 for heating the substrate 201 and heat insulating material 204 areprovided.

After the signal from the load sensor 205 has been detected by apressure detection unit 220 and transmitted to a control unit 221, thecontrol unit 221 controls a pressure adjustment unit 222, causing thepressure detection unit 222 to adjust the flow rate of a valve 223. Inthis way the pressing force of the bonding tool 207 is controlled.

Meanwhile, a conventional bonding apparatus shown in FIG. 10B includes abonding head 300. The bonding head 300 is similar to the bonding head200 shown in FIG. 10A except that a load sensor 205 is arranged on alifting and lowering block 212 beneath a protruding part 210A of abonding tool support 210.

Thus, in the conventional bonding apparatus shown in FIGS. 10A and 10B,there are many parts constituting the lifting and lowering mechanism218, bonding tool support 210, heating mechanism 208, etc. around theposition where the load sensor 205 is provided. For this reason, theload sensor 205 is susceptible to heat generated due to friction ofthese parts; thus the load sensor 205 tends to produce varying valuesfor the detected load. Moreover, since such produced values merelyindicate load acting on the bonding tool 207 itself, the conventionalbonding apparatus cannot find during a bonding operation troubles (e.g.,inclination of the bonding tool, contamination of foreign material,variations in the level of bumps, connection failures betweensubstrate's connection terminals, abnormal lifting and lowering of thebonding tool, and wearing away and/or failure of the lifting andlowering mechanism) like the foregoing bonding apparatus according tothe first embodiment. Accordingly, products obtained using suchconventional bonding apparatus are of less quality than those obtainedusing the bonding apparatus according to the first embodiment, resultingin reduced production yields.

According to the present invention it is possible to solve the foregoingconventional problems and to provide a bonding apparatus capable ofincreasing product quality by realizing high-precision control of apressing force applied upon mounting of an electronic component on asubstrate by bonding, and to a bonding method capable of providinghigh-quality products stably.

The bonding apparatus of the present invention controls pressing forcewith high precision when mounting an electronic component on a substrateby bonding, thereby increasing product quality. Moreover, whenabnormalities have occurred, alarms can be issued and/or the operationof the bonding apparatus can be halted, thus ensuring the traceabilityof products for quality management. For these reasons, the bondingapparatus of the present invention can be suitably used for bonding offlash memories, DRAMs, and FRAMs.

The bonding method of the present invention controls pressing force withhigh precision to achieve stable mounting of an electronic component ona substrate. Thus, with the bonding method of the present invention, itis possible to provide high-quality products with high yields withoutinvolving continued production of defected pieces.

1. A bonding method, comprising: pressing an electronic componentagainst a substrate by means of a bonding head to bond the electroniccomponent to the substrate; detecting a pressure at a bonding surfacebetween the electronic component and the substrate on the basis ofpressure values detected by a plurality of load detection mechanismsthat are substantially equally spaced so as to face one another under asubstrate stage which supports the substrate arranged to face theelectronic component.
 2. The bonding method according to claim 1,wherein the electronic component has a polygonal shape, and the loaddetection mechanisms are disposed at positions corresponding to thecorners of the electronic component.
 3. The bonding method according toclaim 2, wherein the electronic component has a square shape, and theload detection mechanisms are disposed at positions corresponding to thecorners of the electronic component.
 4. The bonding method according toclaim 1, wherein the load detection mechanisms are disposed in a matrixform.
 5. The bonding method according to claim 1, further comprising:adjusting a pressing force of the bonding head; and performing feedbackcontrol on the pressing force while comparing a predetermined referencepressure value with the total of the pressure values detected by theindividual load detection mechanisms.
 6. The bonding method according toclaim 5, wherein in the feedback control step upper and lower thresholdsfor a pressing force on each of the load detection mechanisms arepreviously set on the basis of the pressure values detected by theindividual load detection mechanisms.
 7. The bonding method according toclaim 5, wherein in the feedback control step upper and lower thresholdsfor a pressing force on each row of the load detection mechanisms arepreviously set on the basis of the pressure values detected by theindividual load detection mechanisms.
 8. The bonding method according toclaim 6, wherein the occurrence of abnormality is detected when thepressure value detected by the load detection mechanism has exceeded thethreshold.
 9. The bonding method according to claim 8, wherein theoperation of the pressing step is halted.
 10. The bonding methodaccording to claim 1, wherein traceability is ensured for the bondingstatus of the bonding surface between the electronic component and thesubstrate on the basis of the pressure values detected by the individualload detection mechanisms.